Die-substrate assemblies having sinter-bonded backside via structures, and methods for fabricating such die-substrate assemblies, are disclosed. In embodiments, the method includes obtaining an integrated circuit (IC) die having a backside over which a backmetal layer is formed and into which a plated backside via extends. The IC die is attached to an electrically-conductive substrate by: (i) applying sinter precursor material over the backmetal layer and into the plated backside via; (ii) positioning a frontside of the electrically-conductive substrate adjacent the plated backmetal layer and in contact with the sinter precursor material; and (iii) sintering the sinter precursor material to yield a sintered bond layer attaching and electrically coupling the IC die to the frontside of the electrically-conductive substrate through the backmetal layer and through the plated backside via. The sintered bond layer contacts and is metallurgically bonded to the backside via lining.